JPS61149475A - Manufacture of high purity insulator target - Google Patents

Abstract

PURPOSE:To manufacture a high purity insulator target for forming a high quality insulating thin film having a high dielectric constant by oxidizing or nitriding the surface layer of a high purity metallic target in an atmosphere of a high purity oxidizing or nitriding gas. CONSTITUTION:High purity metallic Ta 102 is fixed on a fixing Ta jig 103 in a quartz reaction tube 101 with Ta screws 104, and a metallic Ta plate 105 is placed in the tube 101 as a counter electrode. High purity gaseous O2 is introduced into the tube 101 from a gas introducing inlet 106 to fill the tube 101 with an atmosphere of high purity gaseous O2 under about 0.1-5Torr pressure. The jig 103 and the Ta plate 105 are connected to a high frequency power source 107, and plasma is generated between the metallic Ta 102 and the Ta plate 105 to oxidize the surface of the metallic Ta 102. By this oxidation a high purity Ta2O5 film 108 is formed on the surface of the metallic Ta 102, giving a high purity insulator target.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a high-purity insulator target, and particularly to a method for manufacturing a high-purity insulator target for forming a high-purity insulating film by sputtering.

[Conventional technology]

Integrated circuits formed on semiconductors, especially silicon semiconductors, are trending toward higher integration and larger capacity, and the memory capacity of integrated circuits such as memory devices has increased from 256 bits to 1M bits or more. ing. In order to increase the capacity of such devices, it is necessary to reduce the chip size as much as possible from the viewpoint of yield and cost, and for this purpose, we are considering circuit systems that are easy to achieve high integration.9Various microfabrication techniques Currently, the development of technology using new materials is progressing, and in IC memories such as dynamic BλM, the information storage section (hereinafter referred to as a cell) is composed of one transistor and one information storage capacitor section. However, in the information storage method using this method, it is the information storage capacity section that occupies most of the semiconductor pellet.For this reason, the dynamic In order to suppress the increase in chip size due to the increase in the capacity of RAM, the most effective means is to reduce the information storage capacity. However, the capacity of this information storage capacity should be approximately 50 fF or more to prevent the effect of memory content loss due to radiation. must be secured. However, if the currently used technology is applied to a 1M to 4M bit RAM, the area of the information storage capacity should be reduced to 5μm.
It is estimated that if a Si film obtained by oxidizing a silicon substrate is used as No. 2, the film thickness will be 30 to 40 mm, and with this film thickness, a tunnel current will flow, so the 5i01 film cannot be used for the information storage capacitor section.

To overcome this problem, Mizohori Capacity Formation Technology is used.

Laminated capacitor formation technology, capacitance formation technology using high dielectric constant materials, and technologies that combine these are considered to be promising alternatives to conventional technology. In particular, the technology for forming an information storage capacitor using a high dielectric constant material is an important technology because it can be applied to integrated circuits that are becoming more densely packed. However, high dielectric thin films are made by thermally oxidizing a silicon substrate to form a film of an element other than silicon on a silicon substrate.
The problem is that it is inferior to gX in terms of leakage current and breakdown voltage.

To solve this problem, it is necessary to study the film deposition method and to control the composition of the film in order to improve the film quality, and for this purpose, a technique for depositing a highly pure film is required.

Film forming methods can be roughly divided into sputtering methods and CVD methods. Since the CVD method uses a compound as a raw material gas, the purity of foreign elements other than the components of the film to be deposited does not increase. Even when using a raw material that does not contain the above-mentioned foreign elements, there are problems such as low vapor pressure of the raw material, safety problems, etc., and problems such as making it unsuitable for practical use or requiring a large-scale equipment for practical use are common.

The sputtering method has the advantage of requiring simpler equipment than the CVD method, since a film can be deposited without a large-scale device once a target is prepared. To form an insulating thin film by sputtering, there are two methods: sputtering a high-purity metal target, depositing it on a substrate, and oxidizing this metal thin film to form an insulating film; In the former case, cracks appear in the film due to volume expansion and grain growth during thermal oxidation, which become current paths and cause leakage. There was a problem that the current increased.

The latter is an effective film deposition method because it can form a film with relatively high density and low leakage current, but the target used here is conventionally formed and sintered by adding a sintering agent called a binder to an insulator. However, because of the binder, it was difficult to increase the purity of the target to 99.91 or higher, and the purity of the film formed on the substrate could not be increased. Furthermore, since the purity was not increased, the reproducibility of the composition when impurities were added was poor, and the reproducibility of the electrical characteristics was also poor. In order to improve the purity of the film, it is necessary to improve the purity of the target, but an effective means to solve this problem has not yet been found.The present invention solves the above-mentioned drawback that target purity does not increase. The purpose of this research is to provide a high-purity insulating film target for forming a high dielectric insulating thin film, which is essential for increasing the density of integrated circuits.

[Means for solving problems]

The method for manufacturing a high-purity insulator target of the present invention is a method for manufacturing an insulator target used when forming an insulating film by sputtering. and oxidizing or nitriding the high-purity metal target in a high-purity oxidizing gas or nitriding gas atmosphere to form a high-purity oxide layer or nitride layer on the surface of the high-purity metal. The process includes the steps of:

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. In this example, metal Ta is oxidized to form a surface OTax Os
t'' sputtering to deposit Ta,0.
Although we will take an example in which the insulating film is formed of an insulating material such as ZrO, the insulating film can also be applied to an insulating material such as ZrO, and the substrate can be similarly applied to a compound semiconductor substrate such as GaAs. FIG. 2 is a schematic diagram of an oxidation device for realizing an insulator target. A high-purity metal Ta102 is placed in a reaction quartz tube 101 in a Ta fixing jig 103.
Fix with manufactured screws 104.

A metal Ta plate 105 is provided as a counter electrode, and the reaction quartz tube 1
01 is reduced in pressure, and the gas inlet 106 is heated to high purity 0. Introduce gas and bring the pressure to 01-5 Torr. Next KT
A high frequency power source 107 is connected between the a electrodes 102 and 105,
Plasma is generated by applying a high frequency of 13.56 h to oxidize the surface of the high purity metal Ta 102 to obtain a target. The high purity metal Ta may be oxidized by thermal oxidation. In this case, oxidation may be performed using O or gas at a temperature of 500° C. or higher.

FIG. 2 shows the structure of an insulating film target obtained by oxidizing Ta102. The structure has high-purity Ta, O, and a film 108 on the 'ratoz. ) Ta10°108 can be grown thick enough, but at least 1000 Å
More than that is fine.

After attaching this target to the target device jig of the sputtering device, high-purity 'ra!
0. [to form. The purity of the formed film is 99.99-
That's all. Low this membrane! Let's do the annealing! 1
) (below 600℃) Conventional leakage current is 10-'A/m2
The one that was about s O-1! , improved to A/-2. 10 g of Ta, O, film on the surface of the metal target 102
When the metal target 102 decreases, ra*0* 108 is grown on the surface of the metal target 102 by taking out the target 102 and subjecting it to variable thermal oxidation, or by placing the target 102 in a sputtering device and subjecting it to plasma oxidation. All you have to do is play the target.

This method provides high-purity, high-dielectric properties with low leakage current *'ra
A tow thin film can be formed.

When adding impurities using the target according to the present invention, a reactive sputtering method can be used. For example, when carbon is added, CO3 and O2 may be mixed into the sputtering gas. Also, when adding nitrogen, N, and O
, gas can be used.

Furthermore, the degree of impurity penetration can be changed by changing the added CO, N, and partial pressures.

This method makes it possible to control the film composition and form a film with controlled properties.

〔Effect of the invention〕

As explained above, according to the present invention, a high-purity insulating film target for forming a high dielectric insulating thin film, which is essential for increasing the density of integrated circuits, can be obtained, and as a result, the film composition can be easily controlled. As a result, it is possible to form a film with a higher density It'', fewer cracks, and higher purity than the conventional film formed by thermally oxidizing after metal sputtering, making it possible to form a high-quality film with less leakage current than before.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a round oxidation apparatus for realizing an insulator target according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram of the structure of an extremely high purity insulator target obtained by the present invention. 101... Reactive quartz tube, 1o2... High purity metal Ta% 103... Tag fixing jig, 1
04...Ta screw, 1o5...Gold J
iTa opposing electrical box, 1o6...Gas inlet, 1
o7... High frequency power supply, 108... High purity ThOf'ii. Agent Patent Attorney Susumu Uchihara: '8$ and Island 4 Lost High Purity Metal T2 High Purity TttxOr Enoki

Claims (1)

[Claims] A method for manufacturing an insulator target used when forming an insulating film by sputtering includes a step of preparing a high-purity metal target, which is the main component of the insulating thin film to be sputtered, and oxidizing or nitriding in an oxidizing gas or nitriding gas atmosphere to form a high-purity oxide layer or nitride layer on the high-purity metal surface. Production method.